Method for extended self-pinned layer for a current perpendicular to plane head

ABSTRACT

A Giant Magneto-Resistive (GMR) sensor ( 900 ) having Current Perpendicular to Plane (CPP) structure is formed providing an extended first pinned layer ( 914 ) as compared to second pinned layer ( 912 ) and free layer ( 910 ). Increased magnetoresistance changes, increased pinning strength, increased thermal stability, and decreased susceptibility to Electro-Static Discharge (ESD) events is realized by maintaining equivalent current densities through free layer ( 910 ) and second pinned layer ( 912 ), while decreasing the relative current density through first pinned layer ( 914 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to spin valve heads for magneticstorage systems, and more particularly to a method and apparatus for anextended self-pinned layer for a Current Perpendicular to Plane (CPP)head.

2. Description of Related Art

Magnetic recording is a key and invaluable segment of theinformation-processing industry. While the basic principles are onehundred years old for early tape devices, and over forty years old formagnetic hard disk drives, an influx of technical innovations continuesto extend the storage capacity and performance of magnetic recordingproducts. For hard disk drives, the areal density or density of writtendata bits on the magnetic medium has increased by a factor of more thantwo million since the first disk drive was applied to data storage.Since 1991, areal density has grown by a 60% compound growth rate, whichis based on corresponding improvements in heads, media, driveelectronics, and mechanics.

Magnetic recording heads have been considered the most significantfactor in areal-density growth. The ability of the magnetic recordingheads to both write and subsequently read magnetically recorded datafrom the medium at data densities well into the Gigabits per Square Inch(Gbits/in²) range gives hard disk drives the power to remain thedominant storage device for many years to come.

Important components of computing platforms are mass storage devicesincluding magnetic disk and magnetic tape drives, where magnetic tapedrives are popular, for example, in data backup applications. Themagnetic disk drive includes a rotating magnetic disk, write and readheads that are suspended by a suspension arm above the rotating magneticdisk and an actuator that swings the suspension arm to place the readand write heads over selected circular tracks on the rotating disk. Theread and write heads are directly mounted on a slider that has anAir-Bearing Surface (ABS) between the slider and the rotating disk. Thesuspension arm biases the slider into contact with the surface of themagnetic disk when the magnetic disk is not rotating. However, when themagnetic disk rotates, air is swirled by the rotating disk adjacent tothe ABS causing the slider to ride on a cushion of air just above thesurface of the rotating magnetic disk. The write and read heads areemployed for writing magnetic data to and reading magnetic data from therotating disk. The read and write heads are connected to processingcircuitry that operates according to a computer program to implement thewrite and read functions.

A magnetoresistive (MR) sensor detects magnetic field signals throughthe resistance changes of a sensing element as a function of thestrength and direction of magnetic flux being sensed by the sensingelement. Conventional MR sensors, such as those used as MR read headsfor reading data in magnetic recording disk and tape drives, operate onthe basis of the anisotropic magnetoresistive (AMR) effect of the bulkmagnetic material, which is typically a perm-alloy. A component of theread element resistance varies as the square of the cosine of the anglebetween the magnetization direction in the read element and thedirection of sense current through the read element. Recorded data canbe read from a magnetic medium, such as the magnetic disk in a magneticdisk drive, because the external magnetic field from the recordedmagnetic medium (the signal field) causes a change in the direction ofmagnetization in the read element, which in turn causes a change inresistance of the read element and a corresponding change in the sensedcurrent or voltage.

In the past several years, prospects of increased storage capacity havebeen made possible by the discovery and development of sensors based onthe giant magnetoresistance (GMR) effect, also known as the spin-valveeffect. In the spin valve sensor, the GMR effect varies as the cosine ofthe angle between the magnetization of the pinned layer and themagnetization of the free layer. Recorded data can be read from amagnetic medium because the external magnetic field from the recordedmagnetic medium, or signal field, causes a change in the direction ofmagnetization of the free layer, which in turn causes a change in theresistance of the spin valve sensor and a corresponding change in thesensed current or voltage.

Magnetic sensors utilizing the GMR effect are found in mass storagedevices such as, for example, magnetic disk and tape drives and arefrequently referred to as spin-valve sensors. The spin-valve sensorsbeing divided into two main categories, the Anti-FerroMagnetically (AFM)pinned spin valve and the self-pinned spin valve. An AFM pinned spinvalve comprises a sandwiched structure consisting of two ferromagneticlayers separated by a thin non-ferromagnetic layer. One of theferromagnetic layers is called the pinned layer because it ismagnetically pinned or oriented in a fixed and unchanging direction byan adjacent AFM layer, commonly referred to as the pinning layer, whichpins the magnetic orientation of the pinned layer throughanti-ferromagnetic exchange coupling. The other ferromagnetic layer iscalled the free or sensing layer because the magnetization is allowed torotate in response to the presence of external magnetic fields.

In the self-pinned spin valve, the magnetic moment of the pinned layeris pinned in the fabrication process, i.e.—the magnetic moment is set bythe specific thickness and composition of the film. The self-pinnedlayer may be formed of a single layer of a single material or may be acomposite layer structure of multiple materials. It is noteworthy that aself-pinned spin valve requires no additional external layers appliedadjacent thereto to maintain a desired magnetic orientation and,therefore, is considered to be an improvement over theanti-ferromagnetically pinned spin valve.

Recent hard disk drive designs have utilized the Current In-Plane (CIP)head, where the sense current travels between the magnetic shieldsparallel to the sensor plate. Such a design yields optimism to sufficeup to areal densities close to 100 Gbits/in², however, research effortscontinue to find even better read heads so that areal densities may beboosted into the many hundreds of Gbits/in² range.

One such discovery is the Current Perpendicular to Plane (CPP) head,whereby the sense current travels from one magnetic shield to the other,perpendicular to the sensor plate. The CPP head provides an advantageover the CIP head because as the sensor size becomes smaller, the outputvoltage of a CPP head becomes larger, thus providing an output voltagethat is inversely proportional to the square root of the sensor area.

One of the candidates for realizing high sensitivity using the CPPstructure is the Tunnel-Magneto-Resistive (TMR) head. In a TMR head, themagnitude of the tunneling current, in the gap between two ferromagneticmetals, is dependent upon the electron's spin directions orpolarizations. The TMR head, however, has several disadvantagesincluding a large resistance due to the barrier layer, which limits theoperating frequency and makes the Johnson and Shot noise high. Abreakthrough in fabrication technology is thus required to lower theresistance of the barrier layer before the TMR head becomes a viable CPPoption.

Another candidate for the CPP structure uses a multilayer GMR structurethat exhibits a large output signal, but has other problems such as thegeneration of hysteresis and the magnetic domains of their read elementsare difficult to control. Moreover, if in-gap type read heads are usedfor high-density recording, the sensor films must be thinner than theread gap.

Other candidates for the CPP structure use a Spin Valve (SV) arrangementfor ultra-high density recording. However, the MR ratio of a CPP elementhaving a conventional SV is a very low percentage and its outputvoltage, which is related to the resistance change, is too low.

It can be seen therefore, that there is a need for an improved CPP headstructure utilizing the SV that exhibits an increased magnetoresistancechange, while maintaining control of its magnetic domain.

SUMMARY OF THE INVENTION

To overcome the limitations in the prior art described above, and toovercome other limitations that will become apparent upon reading andunderstanding the present specification, the present invention disclosesa method and apparatus for extending the self-pinned layer of a CPP GMRstructure to enhance pinning strength, thermal stability, andmagnetoresistance effects.

In one embodiment of the present invention, a method of forming a spinvalve sensor is provided. The method comprises forming a pinned layerthat includes a first pinned layer having a first magnetic orientationand a first width and a second pinned layer having a second magneticorientation anti-parallel to the first magnetic orientation. The methodfurther comprises forming a sensing layer having a second width, wherethe first width is wider than the second width.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity to theclaims annexed hereto and form a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to accompanying descriptive matter, in whichthere are illustrated and described specific examples of a method inaccordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 illustrates a storage system according to the present invention;

FIG. 2 illustrates one particular embodiment of a storage systemaccording to the present invention;

FIG. 3 illustrates a slider mounted on a suspension;

FIG. 4 illustrates an ABS view of the slider and the magnetic head;

FIGS. 5A and 5B illustrate exemplary Current Perpendicular to Plane(CPP) Giant Magneto-Resistive (GMR) head sensors in accordance with thepresent invention;

FIGS. 6A and 6B illustrate basic GMR sensor operation;

FIG. 7 illustrates an exemplary sensing stack according to the presentinvention;

FIG. 8 illustrates an exemplary embodiment of a CPP GMR structureaccording to the present invention; and

FIG. 9 illustrates an alternate embodiment of a CPP GMR structureaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the exemplary embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration the specific embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized as structural changes may be made withoutdeparting from the scope of the present invention.

The present invention provides a method and apparatus that extends thepinned layer of a CPP GMR structure in relation to its free layer. In sodoing, increased pinning strength is realized by maximizingmagnetostriction and compressive stress thus increasing thermalstability. Further, the CPP GMR structure according to the presentinvention increases the change in magnetoresistance through the use ofthe extended pinned layer, while decreasing its susceptibility toelectrostatic discharge events.

FIG. 1 illustrates an exemplary storage system 100 according to thepresent invention. A transducer 110 is under control of an actuator 120,whereby the actuator 120 controls the position of the transducer 110.The transducer 110 writes and reads data on magnetic media 130. Theread/write signals are passed to a data channel 140. A signal processor150 controls the actuator 120 and processes the signals of the datachannel 140 for data exchange with external Input/Output (I/O) 170. I/O170 may provide, for example, data and control conduits for a desktopcomputing application which utilizes storage system 100. In addition, amedia translator 160 is controlled by the signal processor 150 to causethe magnetic media 130 to move relative to the transducer 110. Thepresent invention is not meant to be limited to a particular type ofstorage system 100 or to the type of media 130 used in the storagesystem 100.

FIG. 2 illustrates one particular embodiment of a multiple magnetic diskstorage system 200 according to the present invention. In FIG. 2, a harddisk drive storage system 200 is shown. The system 200 includes aspindle 210 that supports and rotates multiple magnetic disks 220. Thespindle 210 is rotated by motor 280 that is controlled by motorcontroller 230. A combined read and write magnetic head 270 is mountedon slider 260 that is supported by suspension 250 and actuator arm 240.Processing circuitry exchanges signals that represent information withread/write magnetic head 270, provides motor drive signals for rotatingthe magnetic disks 220, and provides control signals for moving theslider 260 to various tracks. Although a multiple magnetic disk storagesystem is illustrated, a single magnetic disk storage system is equallyviable in accordance with the present invention.

The suspension 250 and actuator arm 240 position the slider 260 so thatread/write magnetic head 270 is in a transducing relationship with asurface of magnetic disk 220. When the magnetic disk 220 is rotated bymotor 280, the slider 240 is supported on a thin cushion of air, i.e.,air bearing, between the surface of disk 220 and the ABS 290. Read/writemagnetic head 270 may then be employed for writing information tomultiple circular tracks on the surface of magnetic disk 220, as well asfor reading information therefrom.

FIG. 3 illustrates slider/suspension combination 300 having a slider 320mounted on a suspension 322. First and second solder connections 302 and308 connect leads from the sensor 318 to leads 310 and 314,respectively, on suspension 322 and third and fourth solder connections304 and 306 connect to the write coil (not shown) to leads 312 and 316,respectively, on suspension 322.

FIG. 4 is an ABS view of slider 400 and magnetic head 410. The sliderhas a center rail 420 that supports the magnetic head 410, and siderails 430 and 460. The support rails 420, 430 and 460 extend from across rail 440. With respect to rotation of a magnetic disk, the crossrail 440 is at a leading edge 450 of slider 400 and the magnetic head410 is at a trailing edge 470 of slider 400.

The above description of a typical magnetic recording disk drive system,shown in the accompanying FIGS. 1–4, are for presentation purposes only.Disk drives may contain a large number of disks and actuators, and eachactuator may support a number of sliders. In addition, instead of anair-bearing slider, the head carrier may be one which maintains the headin contact or near contact with the disk, such as in liquid bearing andother contact and near-contact recording disk drives.

FIG. 5A illustrates an exemplary ABS view of CPP GMR head sensor 500 inaccordance with one embodiment of the present invention, excluding theshield, seed, and cap layers typically found with GMR structures.Sensing stack layer 502 is in contact with spacer layer 506, but due tothe width difference between sensing stack layer 502 and spacer layer506, the amount of surface area contact between the two layers isdiminished. Second pinned layer 508 and first pinned layer 512 each haveequal widths as compared to spacer 506 and are separated by couplinglayer 510, which may be composed of a thin layer of a refractory metal,such as Ru. Insulator layers 504 and 514 are in contact with the sidesof sensing stack layer 502 and portions of the top side of spacer layer506.

It can be seen that the width of layers 506–512 are extended beyond thewidth, or active portion, of sensing stack 502, thus increasing themagnetic stability of CPP GMR head structure 500 and itsmagnetoresistive signal producing ability. In general, the width ofsensing stack 502 must be diminished in order to coincide with thediminished track width of the magnetic storage medium (not shown), butthe width of the first and second pinned layers 512 and 508 is notdiminished. Rather, the width of first and second pinned layers 512 and508 is made to be wider than the width of sensing stack 502, in order torealize the advantages of the present invention.

The magnetic stability of first and second pinned layers is directlyproportional to their volume. In other words, when the volume of thepinned layers shrinks, the total magnetic anisotropic field between themalso shrinks because the total magnetic anisotropic field is directlyproportional to the total volume of the pinned layers. Accordingly, astheir volume shrinks, the pinned layers become more susceptible tothermal asperities that may cause their magnetic orientations toreverse. Thus, by maintaining the volume of the pinned layers constantwhile shrinking the width of sensing stack 502, there is nocorresponding reduction in magnetic stability of the pinned layers.

It should be noted that in a first embodiment, second pinned layer 508and first pinned layer 512 are self-pinned. Coupling occurs due to theintrinsic properties of the pinned and coupling layers, such as thepositive magnetostriction and compressive stress properties provided bythe pinned layer composition, e.g., CoFe. Coupling layer 510 negativelycouples second pinned layer 508 and first pinned layer 512 such thatthey are oppositely magnetized in the manner of an anti-ferromagnet. Themagnetic orientations of the first and second pinned layers 512 and 508are anti-parallel to one another and are perpendicular to the ABS asillustrated.

The effective anisotropy field of the three layer structure, i.e.,layers 508–512, is inversely proportional to the difference between thethickness of first pinned layer 512 and second pinned layer 508.Accordingly, when the thickness of pinned layers 508 and 512 is made tobe equal, the effective anisotropy field of the three layer structuremay be maximized.

In a second embodiment, the use of a thicker, e.g., greater than 100angstroms, AFM layer (not shown) below second pinned layer 512 may beused. The effect of using the AFM layer is to exchange couple the firstpinned layer to the AFM layer, while utilizing second pinned layer 508as the reference layer for the spin valve. Using the AFM layer, however,lengthens the read gap of the CPP GMR structure 500 and may not bedesirable in some implementations.

FIG. 5B illustrates an ABS view of an alternative CPP GMR head sensor518 in accordance with another embodiment of the present invention,excluding the shield, seed, and cap layers typically found with GMRstructures. Sensing stack layer 530 is in contact with spacer layer 534,which is in contact with second pinned layer 524. Second pinned layer524 is in contact with coupling layer 526, but due to the widthdifference between second pinned layer 524 and coupling layer 526, theamount of surface area contact between the two layers is diminished.Insulator layers 532 and 522 are in contact with side portions ofsensing stack layer 530, spacer layer 534, and second pinned layer 524,as well as with top portions of coupling layer 526.

Sputtering techniques may be used to create the multilayer, CPP GMRstructures as shown in FIGS. 5A and 5B. Once all layers are in place,etching is performed, either through the use of ion milling or throughthe use of chemical mechanical polishing, to accommodate the insulatorlayers. Aluminum oxide, for example, may be used for insulator layers514, 504, 532, and 522 and may be deposited using a lift off process. Ina first embodiment according to the present invention as shown in FIG.5A, the insulator layers 514 and 504 extend down to spacer layer 506. Ina second embodiment according to the present invention as shown in FIG.5B, the insulator layers 532 and 522 extend down to coupling layer 526.

CPP GMR head structures 500 and 518 are multi-layer structuresexhibiting a GMR effect, whereby a large change in resistance ismeasured depending upon the relative magnetic orientations of theferromagnetic layers within the multilayer as illustrated by FIGS. 6Aand 6B. FIG. 6A illustrates basic CPP GMR head 600 that is in a parallelconfiguration, whereas FIG. 6B illustrates basic CPP GMR head 614 havingan anti-parallel configuration. The parallel configuration is definedwhen the magnetic orientations of the free magnetic layer and the pinnedmagnetic layer are in the same direction, whereas the anti-parallelconfiguration is defined when the magnetic orientations of the freemagnetic layer and the pinned magnetic layer are in opposite directions.In both configurations, shields 604 and 612 act as terminals that areused to couple to sense current source 602, whereby the sense currentpasses orthogonally through each surface of the multilayer.

Free magnetic layers 606 and 616, have their respective magneticorientations set by the magnetic field induced by the magnetic mediabeing read. If a logic “1” has been recorded on the magnetic media,where for example a logic “1” indicates the presence of a magneticfield, then the magnetic orientation of free magnetic layer 606 shown inFIG. 6A may result, thus producing the parallel magnetic configurationsof ferromagnetic layers 606 and 610. If a logic “0”, on the other hand,has been recorded on the magnetic media, e.g., the lack of a magneticfield, then the anti-parallel magnetic configurations of ferromagneticlayers 616 and 618 as shown in FIG. 6B may result.

The GMR effect can thus be summarized by the relative magneticorientations of free magnetic layer 606 and 616 to the respective pinnedmagnetic layers as illustrated by FIGS. 6A and 6B. On the one hand, FIG.6A represents a parallel magnetic orientation, which results in a lowimpedance state of CPP GMR 600. Sense current 602 conducted by the lowimpedance of CPP GMR 600, therefore, results in a low voltage developedacross the shield terminals that may be detected by a volt meter (notshown). On the other hand, the anti-parallel magnetic orientation shownin FIG. 6B, represents a high impedance state of CPP GMR 614, resultingin a high voltage measurement across the shield terminals. Thus, bydetecting the voltage differences induced by the relative parallel andanti-parallel magnetic orientations of the free layer and pinned layers,logic values read from the magnetic media may be ascertained.

FIG. 7 illustrates exemplary sensing stack 700 according to the presentinvention, which illustrates the composition of sensing stack 502 and530 as illustrated in FIGS. 5A and 5B. Cap layer 702 is in contact withAFM layer 704, which is in contact with bias layer 706. Spacer layer 708separates bias layer 706 from free layer 710. The thickness of biaslayer 706 is preferably as thick, or thicker, than that of free layer710. Bias layer 706 is exchange coupled to AFM layer 704 such thatmagnetic moment 712 is parallel to the ABS as shown. Spacer 708 may becomposed of Ru, but may also be composed of, for example, Cu or Tu. Freelayer 708 may be composed of a single layer of CoFe, or alternatively,may be composed of a bi-layer of CoFe/NiFe, where the CoFe layer formsthe bottom layer, which is in contact with spacer 506 or 534, as shownin FIGS. 5A and 5B, respectively. Magnetic moment 714 of free layer 708is pinned anti-parallel to magnetic moment 710 of bias layer 704.

Bias layer 706 provides stabilizing bias to free layer 710, whereby thecombination of bias layer 706 and free layer 710 creates a flux closedstructure. That is to say that bias layer 706, acting as a smallpermanent magnet when it is pinned, creates magnet flux lines inaccordance with the right hand rule. Free layer 710, which is magnetizedanti-parallel to bias layer 706, creates magnetic flux lines inopposition to the flux lines created by bias layer 706. Thus, no strayfields will be produced because there exist no free poles at the ends ofbias layer 706 and free layer 710, since they have been cancelled out.

FIG. 8 illustrates one embodiment of exemplary CPP GMR structure 800 inaccordance with the present invention, where exemplary layercompositions and their corresponding thickness are listed for eachlayer. CPP GMR structure 800 is bounded on both ends by shields 802 and816 having, for example, NiFe composition at a thickness of between 0.5to 2 microns.

The seed layer is comprised of approximately 30 angstroms of Ta,followed by approximately 30 angstroms of NiFeCr, followed byapproximately 8 angstroms of NiFe. In one embodiment according to thepresent invention, the next layer is made up of less than 30 angstromsof PtMn, whereby first pinned layer 814 and second pinned layer 812 areself-pinned as discussed in relation to FIGS. 5A and 5B. In anotherembodiment according to the present invention, the PtMn layer is greaterthan 100 angstroms in thickness, whereby first pinned layer 814 isexchange coupled to the PtMn layer and second pinned layer 812 providesthe reference layer. The PtMn layer may also be made up of, for example,IrMn, at a thickness of between 40 to 80 angstroms. First pinned layer814 and second pinned layer 812 should be made to have substantiallyequivalent thickness between 15 and 40 angstroms and separated byapproximately 8 angstroms of Ru.

Spacer 818 is composed of between 15 and 30 angstroms of Cu separatingsecond pinned layer 812 from free layer 810. In one embodiment accordingto the present invention, Al₂O₃ or MgO barrier layers with thickness inthe range of 3–6 angstroms may also be used for spacer 818, such thatthe sensor operates as a magnetic tunneling sensor.

In one embodiment according to the present invention, free layer 810 ismade up of a single layer of CoFe having an approximate thickness of 30angstroms. In another embodiment according to the present invention,free layer 810 is made up of a bi-layer of NiFe and CoFe, whereby theCoFe layer is adjacent to barrier 818. Biasing layer 806 is made up ofgreater than 30 angstroms of CoFe below between 100 and 200 angstroms ofPtMn. IrMn may be used instead of PtMn at a thickness of about 40–80angstroms. The thickness of biasing layer 806 should be held greater to,or at least equal to, the thickness of free layer 810. Approximately 30angstroms of Ta follows to form the cap of the structure, just belowsecond shield 802.

It should be noted that milling, followed by the subsequent applicationof Al₂O₃ layers 808 and 804, is only taken down to barrier 818, thusincreasing the current density conducted by free layer 810 as comparedto the current density conducted by second pinned layer 812. Asdiscussed earlier, a voltage difference is detected across shields 802and 816 in relation to the change in magnetoresistance that is createdby the electron scattering between free magnetic layer 810 and secondpinned layer 812 across barrier 818. The voltage difference, ΔV, isproportional to the resistance change, ΔR, according to the followingrelation: ΔV˜I_(S)*ΔR, where I_(S) is the sense current flowing throughfree layer 810 and second pinned layer 812. The magnetoresistancesignal, or ΔR, is being generated between free layer 810 and secondpinned layer 812 according to the respective magnetic moments betweenthe two layers as discussed in relation to FIGS. 6A and 6B. However, theamount of ΔR generated is reduced by the reduction in current densitythrough second pinned layer 812.

FIG. 9 illustrates another embodiment of exemplary CPP GMR structure 900in accordance with the present invention, that exhibits increased ΔR.CPP GMR structure 900 is bounded on both ends by shields 902 and 916having, for example, NiFe composition at a thickness of between 0.5 to 2microns.

The seed layer is comprised of approximately 30 angstroms of Ta,followed by approximately 30 angstroms of NiFeCr, followed byapproximately 8 angstroms of NiFe. In one embodiment according to thepresent invention, the next layer is made up of less than 30 angstromsof PtMn, whereby first pinned layer 914 and second pinned layer 912 areself-pinned as discussed in relation to FIGS. 5A and 5B. In anotherembodiment according to the present invention, the PtMn layer is greaterthan 100 angstroms in thickness, whereby first pinned layer 914 isexchange coupled to the PtMn layer and second pinned layer 912 providesthe reference layer. The PtMn layer may also be made up of, for example,IrMn, at a thickness of between 40 and 80 angstroms. First pinned layer914 and second pinned layer 912 should be made to have substantiallyequivalent thickness between 15 and 40 angstroms and separated byapproximately 8 angstroms of Ru.

Spacer 918 is composed of between 15 and 30 angstroms of Cu separatingsecond pinned layer 912 from free layer 910. In one embodiment accordingto the present invention, Al₂O₃ or MgO barrier layers with thickness inthe range of 3–6 angstroms may also be used for spacer 918, such thatthe sensor operates as a magnetic tunneling sensor.

In one embodiment according to the present invention, free layer 910 ismade up of a single layer of CoFe having an approximate thickness of 30angstroms. In another embodiment according to the present invention,free layer 910 is made up of a bi-layer of NiFe and CoFe, whereby theCoFe layer is adjacent to barrier 918. Biasing layer 906 is made up ofgreater than 30 angstroms of CoFe below between 100 and 200 angstroms ofPtMn. IrMn may be used instead of PtMn at a thickness of about 40–80angstroms. The thickness of biasing layer 906 should be held greater to,or at least equal to, the thickness of free layer 910. Approximately 30angstroms of Ta follows to form the cap of the structure, just belowsecond shield 902.

A particular advantage of CPP GMR structure 900 over that of CPP GMRstructure 800 is achieved by increasing the amount of magnetoresistancesignal, or ΔR, that is produced. It should be noted that the width ofsecond pinned layer 912 is substantially equal to the width of freelayer 910. This condition is implemented by milling down through barrier912, followed by subsequent application of Al₂O₃ layers 908 and 904. Insuch an embodiment, the current density conducted by free layer 910 andsecond pinned layer 912 is equivalent. Therefore, the amount ofmagnetoresistance signal, or ΔR, is maximized because current densityhas not been decreased through the magnetoresistance producing layers,i.e., free layer 910 and second pinned layer 912. Further, ΔR increaseis realized by maintaining the original width of first pinned layer 914,thus reducing its relative current density, thus reducing its negativecontribution of ΔR.

As mentioned above, the present invention provides a method andapparatus for providing enhanced magnetoresistance signal generation,increased pinning strength, and increased thermal stability due to theextended pinned layer structure. The structure also provides robustbehavior when exposed to Electro-Static Discharge (ESD) events becausethe current density in the pinned layer is reduced by its extendedstructure, thereby reducing the temperature increase caused by the ESDevent.

According to the present invention, the fields of computers and magneticdata storage and recovery are improved by the formation a CPP GMR sensoras disclosed herein. Thus, the present invention improves not only thefield of GMR sensors, but also the entire field of computers andmagnetic data storage and retrieval.

The foregoing description of the exemplary embodiment of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not with this detailed description, but rather bythe claims appended hereto.

1. A method of forming a spin valve sensor, comprising: forming a firstpinned layer with a top surface, bottom surface and sides orthogonal tothe top and bottom surface and having a first magnetic orientation and afirst width; forming a second pinned layer with sides orthogonal to thetop and bottom surface of the first pinned layer and having a secondmagnetic orientation anti-parallel to the first magnetic orientation anda second width; forming a sensing layer with sides orthogonal to the topand bottom surface of the first pinned layer and having a third widthsmaller than the first width; and forming a spacer layer with sidesorthogonal to the top and bottom surface of the first pinned layer andhaving a width equal to the second width; wherein the third width isselected to coincide with a predetermined track width, the first widthbeing selected to be wider than the predetermined track width.
 2. Themethod according to claim 1, further comprising forming a coupling layerdisposed between the first and second pinned layers.
 3. The methodaccording to claim 2, wherein the first and second pinned layers areformed with substantially equal thickness.
 4. The method according toclaim 3, wherein forming the first and second pinned layers createsself-pinned magnetic orientations.
 5. The method according to claim 3,further comprising depositing an anti-ferromagnetic material (AFM)adjacent to the first pinned layer, wherein a thickness of the AFMcreates exchange coupling between the AFM and the first pinned layer. 6.The method according to claim 1, wherein forming the sensing layerincludes: forming a free layer having a third magnetic orientationorthogonal to the first and second magnetic orientations; forming a biaslayer in proximity to the free layer having a fourth magneticorientation anti-parallel to the third magnetic orientation; and formingan AFM layer adjacent to the bias layer, wherein exchange couplingbetween the AFM layer and the bias layer sets the fourth magneticorientation.
 7. The method according to claim 6, wherein the bias layeris formed with a thickness greater than a thickness of the free layer.8. The method according to claim 1, wherein the second pinned layer isformed with a width substantially equal to the third width.
 9. Themethod according to claim 8, wherein insulating layers are disposed onboth sides of the second pinned layer.
 10. The method according to claim1, wherein the second pinned layer is formed with a width substantiallyequal to the first width.
 11. The method according to claim 1, whereininsulating layers are disposed on both sides of the sensing layer.